WxSat

Short for Weather Satellite. This combines the radio and computing hobbies rather well. Receiving WxSat images is fairly easy, and there are a few satellites wizzing around the world that transmit some nice pictures. When the coulds clear you can sometimes see the outline of the UK!

Please note that as of 2019, the use of the APT analog transmission is almost non-existant. At this time, there are only three satalites left transmitting this form of image data. So I have not been activly receiving for quite some time now.

NOAA 15 Frequency 137.6200 Mhz (Showing signs of sync issues)

NOAA 18 Frequency 137.9125 Mhz

NOAA 19 Frequency 137.1000 Mhz

The transmissions of newer satalites have moved to a wide bandwidth system, and there are non-commercial ways to receive this data - the Group for Earth Observation GEO is a good source of information on this subject.

Historically, all you need to receive WxSat pictures is a suitable receiver, some decoding software, and an antenna. The most common transmission format is called A.T.P. (Automatic Picture Transmission) this is a modified FAX style transmission.

Receivers can be almost anything from handie-scanners to custom built WxSat receivers. Almost anything that can receive in the 137Mhz sat band will get something. My setup is unusual in that I use the Amiga to decode the images. Decoding software is availabe for most computers, ranging from free to expensive. Just to give you an idea of what you can receive, here is an image I took back in 1993, one of the few images I have when it was nice and sunny over the UK!

The receiving system I use is:

RX ICOM R9000 - Wide FM (30Khz) AFC on,
JIM General Purpose pre-amp (latterly a mast-head pre-amp rather than the JIM)
Ant H/Brew Tall thin QFH approx 30ft upo - site located abt 15Km from centeral London
Software WxtoImg linux.

Note that I suffer from very very bad wide band noise, which normally means that sat reception is wiped out. Sometimes I the noise goes away and I get good images. High power radio pager transmitters are the main culprits. In the NOAA18 image below there is only one big pager burst in this image. Apart from despecle and adding the outlines, this image is "as is"

NOAA 19

Noaa 19 was launched on Friday 6th Feb 2009, and is the last of this series of satalites. This sat, has had a "interestiung" life, as it fell off the support table as it was being rotated. The cause was that the hold down bolts had been removed. The sat had to be extensivly rebuilt. However as it was the last in the series, many of the stockpiled and unused spares were available for use.

Note that at this time, NOAA 19 was transmitting two visable light images, this continued for several weeks untill the IR sensors were fully cooled and out-gassed. Once this was done, the transmission reverted to the "normal" IR and Vis image side by side.

The images below are from two passes over the UK on Sunday 8th Feb, one pass at 12:52, and the other (and better) pass at 14:34.

08 1Feb 2009 2:52 pass:

This pass was a little to the east of the UK, and as you can see the UK is still in the grip of some rather chilly weather, with a lot of cold cloud cover. Also note the very poor reception to the south. N Africa is there, but the image is very noisy. This is due to two things. The first is that the antenna is screened slightly in that direction, and that there is a powerful paging transmitter on a nearby frequency that tends to degrade and desense the receiver.

The poor coverage to the north is due to a "hill" (Part of the A13 where it crosses a railway) and several tall buildings obstructs the signal.

08 Feb 2009 14:34 pass:

This pass was well to the west of the UK and the first thing to note is that the coverage to the south is much better, purely due to the antenna having a clear view to the west. Also note the darker band at the bottom, extending up to the first white bar in the greyscale strip on the left hand side. This demostrates the difference between a receiver with a 15Khz filter. The dynamic range is reduced quite a bit. When I switched to the 30Khz filter the difference is very marked.

08 Feb 2009 14:34 pass (2nd image):

This is the same image as the previous, but without the map overlay, and also processed with the "prestine" options of the WxToImg software. The bandwidth change is even more pronounced.

12 Feb 2009 13:53 pass.

As NOAA 19 is still in the checkout phase, (the IR sensors are still being outgassed etc) it sends two vis light images. This allows for an enhancement not normally seen, which brings out vegiation rather more clearly. Of course the colours are all false...